The present invention relates generally to rotary piston internal combustion engines and more particularly to improvements in the structure of such engines whereby stratification of the combustion chamber charge may be effected. More specifically, the invention relates to means whereby a stratified charge, consisting of an air lamina and of a lamina of air-fuel mixture, may be obtained.
In a rotary piston internal combustion engine of the conventional type, a combustible charge ignited by a spark plug spreads rapidly through the combustion chamber of the engine toward the leading side of the chamber taken with respect to the direction of rotation of the rotor. However, it has been found that the ignited charge does not satisfactorily permeate the trailing side of the combustion chamber taken in a direction rearwardly of the direction of rotor rotation. As a result, conventional rotary engines give rise to serious problems related to incomplete combustion which tends to occur in the trailing side of the combustion chamber resulting in increased fuel consumption as well as increase in the detrimental components, such as HC, CO, etc. contained in the unburned exhaust gases thereby causing increased air pollution.
However, rotary engines have been found to involve an inherent characteristic feature giving rise to a gas flow effect within the combustion chamber resulting from rotation of the rotor. Since the gas flowing into the combustion chamber tends to flow along with the rotor as it rotates, a graded air-fuel mixture may be charged into the combustion chamber. In the operation of the engine, dense and light strata which are matched with the graded air-fuel ratio of the mixture can be maintained within the combustion chamber even during the decompression stroke.
In an attempt to overcome the aforementioned problems by utilization of inherent characteristics of the rotary engine, there has been heretofore proposed provision of two ports in the suction system of the engine, with one port being utilized for charging a denser air-fuel mixture into the combustion chamber with the other port being utilized for charging air. Provision of these ports makes it possible to feed and stratify, respectively, the denser mixture toward the leading side of the combustion chamber with the air being provided in the trailing side of the combustion chamber. As a result, the tendency toward incomplete combustion is diminished in the trailing side of the combustion chamber where the ignited flame would otherwise spread nonuniformly.
In accordance with a typical known approach utilizing this concept, one of the ports of the suction system is provided in the side wall of the rotor housing and it is opened or closed in accordance with passage thereover of the engine side seal provided on the engine rotor. As a result of this arrangement, gas from the side port is directed into the combustion chamber from a direction extending perpendicular to the direction of rotor rotation, i.e. in a direction parallel to the axis of rotation of the rotor. As a result, the gas introduced from the side wall of the rotor housing will collide with gas already present in the combustion chamber thereby causing increased turbulence within the chamber at the time of charging. Consequently, it has been found extremely difficult to effect distinctive stratification of the gases contained within the combustion chamber.
The present invention is directed primarily to provision of a solution for this problem by adapting the structure of a conventional rotary engine to provide an improved mode of operation whereby a denser air-fuel mixture together with air may be charged into the combustion chamber separately thereby to effect distinctive, stable stratification in lamina form of the charge within the combustion chamber.